The article “Towards quantitative PET/MRI: a review of MR-based attenuation correction techniques” by Matthias Hofmann et al., European Journal of Nuclear Medicine and Molecular Imaging, 36 Suppl 1: pages S93 to S104 (2009) discloses a combined positron emission tomography (PET) and magnetic resonance (MR) imaging system, which produces an attenuation map based on a generated MR image acquired by an MR data acquisition unit. The attenuation map is used for reconstructing an attenuation-corrected PET image.
The field of view (FOV) of the MR image can be limited, which may truncate the MR image at the perimeter particularly for larger persons. Moreover, an MR image can be distorted due to, for example, metal implants or ports. These restrictions to the quality of the MR image can also reduce the quality of the attenuation map produced by using the MR image.